In recent days, communication traffic relayed by a relay device like a repeater increases with significant increase of the number of wireless terminal devices. Accordingly, there is proposed a distributed wireless communication system which allows a wireless terminal device to select at least one relay device among plural relay devices which are connected one another by a predetermined communication line when the wireless terminal device communicates with another wireless terminal device. In such wireless communication system, each wireless terminal device calls through a channel of a repeater to establish a communication path with a communication-counterparty wireless terminal device. The repeater notifies information indicating whether or not the current channel is busy or idle to wireless terminal devices in an area through a communication frame which is a unit of radio signal.
For example, according to patent literature 1, a communication frame includes a synchronization word, channel identification information, control information and random-access control information, and it is distinguished based on the channel identification information whether contents of the control information are a notification message which must be notified to a wireless terminal device or are an idle message which does not need to be notified thereto. The wireless terminal device which receives the channel identification information performs, when detecting that the control information is the idle message from the channel identification information, such intermittent reception as stopping receiving a frame while the control information is being as the idle message.
Because the idle message indicates the state in which a communication is not relayed between wireless terminal devices, i.e., the state of an idle channel, the wireless terminal device can detect whether or not a current channel is idle or busy.
Patent Literature 1: Unexamined Japanese Patent Application KOKAI Publication No. 2006-93869